Carlfriesite is a rare tellurium mineral with the formula CaTe4+2Te6+O8, or more simplified: CaTe3O8.

It is found associated with cerussite, chlorargyrite, argentian gold, cesbronite, calcite, dickite, baryte, bornite, galena, hessite and tlapallite.

Carlfriesite was found to be synthesizable by heating a mixture of CaO, Te(OH)6 and TeO2 to 150–240°C with water at the vapor pressure of the system.

The resulting material was very fine-grained and colorless, consisting of aggregates of tiny carlfriesite plates.

The material mostly consisted of carlfriesite, but also contained 10–15% paratellurite, as determined by X-ray diffraction.